The first of the four Riachuelo-class submarines of the ProSub program was commissioned by the Brazilian Navy. The S Riachuelo (S40) is a Brazilian Riachuelo-class submarine built for the Brazilian Navy by DCNS in Cherbourg and ICN in Itaguaí, Brazil. The Riachuelo is the seventh boat of the Brazilian Navy to receive this name, in honor of the Battle of the Riachuelo, which took place in 1865, in the Paraguayan War. The ceremony took place at the Itaguai Naval base. The lead boat is a diesel-electric attack submarine (SSK) that will operate off the Brazilian coast to support the protection of a 5.7 million km² area known as the Blue Amazon.
In 2008, Brazil purchased four enlarged Scorpènes for USD 10 billion with a total technology transfer agreement and a second agreement to develop the first Brazilian nuclear-powered submarine, Álvaro Alberto. The hull of Riachuelo was laid down at Cherbourg, France on 27 May 2010 and it was jumboized at the Brazilian Navy Shipyard in Itaguaí in late 2012. Riachuelo was launched on 14 December 2018, and began sea trials in September 2019, the Humaitá was launched on 11 December 2020. This submarine was designed to replace the ageing Tupi and Tikuna-class systems and was acquired under the PROSUB programme.
The first stage of construction of the submarine took place in France, at the headquarters of DCNS in Cherbourg, with the cutting of the first steel plates of the structure. At this point, technology transfer from French technicians to Brazilians began. In the middle of 2013, internal parts manufactured in France arrived, which were then integrated to the other parts built in Brazil. In September 2015, the first construction stage was completed, with the delivery of the last section of resistant hull. The Brazilian Navy noted that it will increase ‘the deterrent power of the Brazilian Armed Forces’.
The Brazilian boats are larger in length, tonnage and cargo capacity compared to the original French Scorpène-class which they are derived of. The Brazilian version are 70.62 m (231.7 ft) and 1,900 tons, compared to the original Scorpènes that are 61.7 m (202 ft) and 1,565 tons. The Riachuelo-class submarines are based on the Scorpene design from French shipbuilder Naval Group and feature six 533 mm torpedo tubes that can host F21 torpedoes or Exocet SM39 Block 2 Mod 2 anti-ship missiles. The other boats of the Brazilian class are Humaitá (S41), Tonelero (S42) and Angostura (S43).